Process of making dry alkaline sulfates.



PATENTED MAY19, 1903.

' S. TRIVIGK. PROCESS OF MAKING DRY ALKALINE SULFATES.

APPLIOATION FILED JUNE 7, 1902.,

N0 MODEL.

INVENTOR WITNLSSES -7m 7 ATTORNEYS PATENT .Patented May 19,-19osi OFFICE.

SIDNEY TRIVIGK, OF CLAPHAM, ENGLAND.

PRocEssoF MAKING DRYALKALINESU'LFA'TES;

SPECIFICATION forming part of Letters Patent N 0. 728,335, dated May 19, 1903. Application filed June 7,1902. erial No. 110,689. (No specimens.)

manufacture of a salt of one or more of the.

alkali metals which contains not less than four chemical units of sulfuricanhydride to one unit of the oxid of the alkali metal and which salt is associated with not more than three chemical units of water of crystallization.

It consists in adding to concentrated sulfuric acid a quantity of a salt of one or more of the alkali metals which has previously been rendered completely anhydrous, subjecting the mixture for some time to a temperature not exceeding 250 centigrade, and asubsequent treatment of the product to a drying process whereby a large proportion of the water of crystallization is extracted.

As a representative example I will describe in detail the process as carried out when the alkali salt consists of common saltchlorid of sodium. This salt is first heated until it is rendered completely anhydrous. A quantity of concentrated sulfuric acid is then placed in a vessel capable of withstanding the action of the heated acid, and arrangements are provided for heating the vessel and withdrawing its contents,and forcollecting and condensing,

' when desired, the volatile products given off in the process. An apparatus such as is used in the production of hydrochloric acid would serve the purpose of this operation. Such an apparatus is illustrated in the accompanying drawings, in which- I Figure l is avertical section. Fig. 2 is a section taken along the broken line 2 20f Fig.

- 1. Fig. 3 is a sectional plan taken along the line 33 of Fig. 1, in which the pan 0!, is supposed to be removed for the purpose of ex- .hibiting, the flues.

is burned in the body 0, and the products of ofthe furnace.

combustion pass through apertures dd, provided in the arch-which forms a continuation They emerge into the space below the center of the pan and proceed along.

the annular flue in the direction, shown by the arrows and escape to the chimney by an opening which is indicated in Fig. 3 by the dotted lines e e. The pan is charged through the opening f, the flid g being removed and the sloping hinged door hlowered. The con centrated sulfuric acid is first supplied by a pipe whichis afterward withdrawn, and then the appropriate quantity of anhydrous salt is placed on the sloping door h, which at this time is closed, and then the lid 9 is replaced. By opening the door it at intervals to a small amount only by means oftheweighted lever I the salt" is fed into the acidin a gradual manner. 9

,If the salt is chlorid of .sodium', there will bean abundant evolution of hydrochloricacid gas, which will escape through thepipe l to a condenser, the hydrochloric acid being a by-product. The heat evolved in this operation is'sufficientto raisethe temperature of the mixture to the required degree without the aid of external heat; butlit is advantageous to employsome external heat to main tain the molten condition. When niter cake is used or other-salts, external heat is essential to the process. The temperature to which the mixture is subjected is short of that which will cause the evolutionv of sulfuric-acid fumes, which is about 250 centigrade. v

When the operation is completed, a vessel mounted on wheels is run in through the doorway m, so as to be below the center of the pan. The plug n is then withdrawn and the pan emptied of its contents, the salt being then in the molten state.

If allowed to cool at rest, it will produce a ICO form the tetra-sulfate simply will be 29.8 per cent., for the equation which expresses the reaction is The 1101 is evolved as vapor, and the product left in the vessel has a composition in which the combining elements may be regarded as grouped, so as to form sodium oxid, (Na O,) sulfuric anhydrid, ($0 and water, (H O,) in which, combined with one chemical unit of Na O, there are four chemical units of S0 and these are associated with three units of water of crystallization.

In practice it would bogadesirable to use a smaller proportion of chlorid on account of the probable loss of some of the H 80 in the subsequent heating and also to provide for the formation of sulfates higher than the tetra-sulfate.

The molten product is well stirred while it is cooling, so as to produce a granulated mass with a large extent of surface. This is exposed to a current of warm air. To facilitate this operation, the granulated mass may advantageously be placed in a revolving cylinder, by which means continually-fresh surfaces will be presented to the warm atmosphere and the extraction of the water of crystallization rendered rapid. By such means I am able to produce a very portable dry salt from which by the addition of water I am able to derive the benefit due to a supply of strong sulfuric acid without having to incur the danger due to its transport.

If Nordhausen orfuming sulfuric acid is used, a larger proportion of sulfates higher than the tetra-sulfate will be secured in'the product; but in this case the heating must be carefully regulated, so as to avoid as much as possible the loss due to the escaping fumes of sulfuric acid.

In the case in which the alkali salt used is chlorid of sodium the subsequent heating is not essential for the formation of tetra-sulfate merely. Heating to a moderate degree appears to encourage the formation of still higher sulfates.

To produce the higher sulfate of potassium in a similar way, probably the most advantageous potassium salt to add to the sulfuric acid would be so-called niter cake, which in the pure anhydrous condition would be represented by K 80 The chemical reaction which in this case would take place if only the tetra-sulfate were formed may be represented by the equation so that the proportions requisite for the complete reaction would be 59.2 of K 80 to 100 H 80 In practice the proportion of the former should be less for the same reasons as those mentioned in the case of sodium.

In the case of potassium salts the reaction should be stimulated by heating during the mixing process. The granulated potassium of crystallization.

product on being exposed to warm air behaves in a similar manner to the sodium salt and parts with a large quantity of its water It may be observed that in the two cases cited in which NaOl and K 80 are used for mixing with the concentrated sulfuric acid the quantity of the salt of the alkali metal which is required to effect the tetra-sulfate reaction is such that there shall be one chemical unit of the alkali metal itself introduced into the mixture for every two chemical units of sulfur which it contains, including the sulfur, if any, which is added with the salt. This condition is required to be satisfied whatever he the salt of alkali metal which is used.

On attempting to similarly produce ammonium tetra or higher sulfates, a somewhat gelatinous mass is formed when cold. Therefore for the purpose of obtaining a dry salt as the final product it will be advantageous to add some sodium or potassium salt with the ammonium salt to the sulfuric acid, and thus obtain a double or treble tetra-sulfate compound mixed with higher sulfates which, with sufficient sodium or potassium, will granulate and subsequently readily part-with its water of crystallization in thedrying process. Adouble salt of sodium and potassium without ammonium may correspondingly be formed.

I claim- 1. A process for the production of a dry salt composed of one chemical unit of an oxid of an alkali metal chemically united with not less than four units of sulfuric anhydrid and associated with not more than three chemical units of water consisting in adding to concentrated sulfuric acid, H 80 free from water, such a quantity of an anhydrous salt of the alkali metal as will contain half as many chemical units of the metal itself as there will be of sulfur in the mixture, heating the mixture to a temperature not exceeding 250 centigrade granulating the mass by stirring while cooling and subsequently exposing it to a current of warm dry air, substantially as described.

2. A process for the production of a dry salt composed of Na O chemically united with not less than four units of S0 and associated with not more than three units of H 0 consisting in adding to concentrated sulfuric acid, H,SO free from water, such a quantity of anhydrous salt of sodium as will contain half as many chemical units of sodium as there Will. be sulfur in the mixture,heating the mixture to a temperature not exceeding 250 centigrade granulating the mass by stirring while cooling and subsequently exposing it to a current of warm dry air,substantially as described.

3. A process for the production of a dry salt composed of Na O chemically united with not less than four units of S0 and associated with not more than three units of H 0, con sisting in adding to one hundred parts of conoentrated sulfuric acid, H 80; free from wa-' ter, nearly thirty parts of anhydrous sodium chlorid, heating the mixtureio a temperature not exceeding 250 centigrade granulating the mass by stirring while cooling and sub-'-- sequently exposing it'to' a current of warm dry air, substantially as described.

4. A process for the production of a dry salt composed of Na O chemically united with not less than four units of S0 and associated with not more than three units of H 0, consisting in adding to concentrated sulfuricacid, H 80 free from water, such aquantity Witnesses:

WALTER J. SKERTEN, ROBT. A; BLAKE.

SIDNEY TRIVIGK. 1 L y i' 

